The plan (maybe rumored) was to release MP first then the story later. Given that the story was only being written recently, the multiplayer might actually be ready to go by now. I could realistically see either an open beta for the MP or even a full MP release with SP to follow. With it all being on Game Pass, it really doesn't matter too much.

Fortnite route was to make free-to-play "singleplayer" with co-op elements, and thats it. After PUBG become popular, they just got lucky as they have base game that easily allowed them to build Battle Royale mode.

Considering MP is a living and breathing ecosystem receiving constant updates and changes and what is played in the long haul, it really doesn't matter too much when you release it. Look at all MS games nowadays starting from Halo 5 all the way up to FH4. They all have weekly and monthly multiplayer updates. Crackdown 3 could just be a strong game pass title because of how it could be updated often.

What I’m saying is at one point they were going to release separately but the games been delayed like 5 times since then so who knows what the situation is now? They’ve only said “Crackdown 3” for the past year or so and haven’t mentioned a split release since that one first announcement.

If it’s following the previous Crackdown games there will be a narrative, but it won’t be a heavy focus and the game will be more of an open world action sandbox. You’ll progress through a story, but that’s unlikely to be the games focus.